This disclosure generally relates to the field of patient monitoring and, more particularly, to systems and method for monitoring and assessing cardiac arrhythmias.
Currently available patient monitoring systems including electrocardiographs (ECG) typically have algorithms for detecting and identifying various arrhythmias. One very common and sometimes critical arrhythmia is atrial fibrillation (AFIB). AFIB is the most common cardiac arrhythmia resulting in hospitalization in the United States. AFIB is often identified by irregular heart rhythm and is clinically defined as uncoordinated contractions of the atria. With critically ill patients AFIB may be serious due to week circulation of the blood during the arrhythmia. In these cases, immediate action by caregivers may be needed. Patients often experience palpitations and have an increased risk of stroke. AFIB puts patients at significant risk because it allows blood to pool and stagnate in the left atrium and, thus, form a clot. This clot can slough off and travel up to the brain where it can block sufficient blood flow to a portion of the brain where upon it will begin to die, thus causing a stroke. AFIB is estimated to cause up to a quarter of all strokes and is often undetected until a stroke occurs. It is estimated that approximately a third of patients experiencing AFIB are asymptomatic.
AFIB requires aggressive treatment. The longer a patient is in AFIB, the more likely they are to remain in AFIB, making early detection desirable. Prompt detection of the onset of AFIB provides an opportunity for therapy during the first 48 hours when expensive antithrombolic treatments may not be necessary because the formation of blood clots has not yet occurred in the atria. The prevalence of AFIB is high and age dependent, from 0.7% in the ages 55-59 to 17.8% for 85 years or older. Yet, AFIB is notoriously hard to detect. The most common method for automatically detecting AFIB in ECG recordings relies heavily on the fact that AFIB is a chaotic atrial arrhythmia, randomly conducted to the ventricles. As such, the time periods between features of the QRS waves, as measured by the RR intervals, should be continuously varying in the presence of AFIB. It is this attribute of AFIB, that it is a continuously chaotic rhythm, that is used by most ambulatory ECG analysis programs to detect AFIB. However, RR intervals of normally conducted beats can vary for other types of benign arrhythmias that are not AFIB. Examples include premature atrial complexes (PACs) or sinus arrhythmia (SA), which are both quite common in the normal population. While these benign arrhythmias do exhibit as variability in RR intervals, these arrhythmias are typically benign and do not pose a serious health concern.